1. Field of the Invention
The present invention relates to the field of blade control devices of ground leveling machines, such as bulldozers and motor graders.
2. Description of the Prior Art
Ground leveling construction machines equipped with the device for controlling the height of the blade automatically based on the laser beam projected at a specified height above the ground are currently in use.
For performing the ground leveling work using such construction machine, topographic survey is executed before and after the ground leveling. Since a laser leveling (staff) rod, transit, or the like surveying equipment has been used for the topographic survey, a great deal of time and labor has been required.
On the other hand, the vehicle is often obliged to stop running due to increased blade load, while the ground leveling is performed with the level of the blade being controlled. In such case, in the prior art, first the blade load is reduced lifting the blade using a blade height setter, and then the blade is lowered. At this time, since the original blade height can no longer be known, the method involves inconvenience that difference occurs between the ground levels before and after the blade manipulation.
The primary object of the present invention is to provide a blade control device equipped with the topographic survey function capable of performing topographic survey while the aforementioned ground leveling construction machine is run.
To achieve the above object, the present invention uses the deviation in the light (beam) receiving position of the light receiving unit (or the photosensor assembly) as a command value of the light receiving device control system during the topographic survey, and the contour is surveyed by detecting changes in height of the light receiving device which follows the laser beams.
Through such arrangement, topographic survey can be performed simply and efficiently without using special surveying equipment such as the laser staff and transit.
Another object of the present invention is to provide a blade control device capable of returning the blade automatically to the original position, even after the height of the blade is changed manually interrupting said automatic leveling.
To attain this object, the present invention provides two command value setting means in the light receiving device control system which controls the height of the light receiving device, and switch elements which selectively supply command values set by said two command value setting means to said light receiving device control system.
The novel features which are believed to be characteristic of the invention, together with further objects, will be better understood from the following description in connection with accompanying drawings in which presently preferred embodiment of the invention is illustrated by way of example.